Device for varying the current flow in an electric circuit



1940. L R.L WILCOX 2,186,222

DEVICE FOR VARYING THE CURRENT FLOW'IN AN ELECTRIC CIRCUIT Filed June17, 1938 I5 Sheets-Sheet 2 Sara. 3!

jndmrg- J h w 07M I Jan. 9, 1940. R w co 2,186,222

DEVICE FOR VARYING THE CURRENT FLOW IN AN ELECTRIC CIRCUIT Filed June17, 1938 s Sheets-Sheet 1 wlw 1940- R. 1., WILCOX 2,186,222 DEVICE FORVARYING THE CURRENT FLOW fN AN ELECTRIC CIRCUIT Filed Jun 17, 1958 5Sheets-Sheet 3 I"IIIIIOOII0 Jmerzfor mass Jan. 9, 1940 UNITED STATESPATENT OFFICE DEVICE FOR VABYING THE CURRENT FLOW IN AN ELECTRIC CIRCUITRobert L. Wilcox, Wilmington, DeL, accignor to Willard L. Morgan,Edrcwood, B. 1.

This invention relates to a novel device for varying the current flow inan electrical circuit and, more particularly, to a novel device forcausing the current in said circuit to vary at a sensible rate from apredetermined low value to a predetermined maximum value and vice versaand to repeat this operation cyclically and automatically.

The principal object of the invention is to provide a novel device ofthis character which is simple in construction, economic to manufactureand operate, and highly efiicient in operation.

Another object of the invention is to provide a device comprising one ormore units, each of which controls one or more electrical circuits, andeach of which comprises a current-regulating device controlled by aspace discharge device whose operation is cyclically varied by alternateenergization and deenergization of such device.

A further object of the invention is to provide a device of thischaracter employing a reactor comprising a saturable magnetic core forregulating the current fiow in the circuit being controlled, the saidcore having associated therewith a winding controlled by the spacecurrent of the space discharge device, whereby the saturation of themagnetic core is controlled by the space discharge device.

A still further object of the invention is to pro vide a device of thischaracter wherein the-alternate energization and deenergization of thesaid space discharge device is effected by me'ans of a relay controlledby the space current of the discharge device.

Other objects and features of the invention will appear hereinafter.

In the accompanying drawings:

Fig. 1 is a diagrammatic illustration of a twounit. or two-stage deviceconstructed according to the invention;

2 is a similar illustration of a modification; and

Fig. 3 illustrates a further modification.

Referring to Fig. 1, there are provided two similar control devices orunits designated respectively A and B adapted to control difierentworking circuits or load circuits. In any instance, the completeapparatus may be composed of any desired number of these units. Theapparatus 5o illustrated employing two units has been chosen arbitrarilyto disclose the invention.

Each of the control devices or units comprises a current regulator inthe form of a saturable magnetic core C1 or C: which, together with its4 associated windings, comprises a variable reactor serving to controlthe current flow in the associated load circuit. Each device or unitcomprises further a space discharge device V1 or V2 and a relay R1 orRz'novelly arranged to control the associated current regulating device,as de- 5 scribed hereinafter.

Each of the current-regulating reactors preferably comprises a magneticcore having two outer legs and an inner leg as illustrated, the corebeing formed of any magnetic material, 10 such as iron or steel,suitable for the purpose in view. On the respective outer legs of thecore, there are provided windings l and 2 which are serially connectedwith one another and are included in the working or load circuit to becon- 15 trolled. In the specific illustration, the windings I and 2 areincluded in circuit with parallel connected load devices 3 and 4 whichmay take the form of lamps. Each of the load circuits controlled by thedevicesor units A and B is ener- 2o gized by supply conductors 5 whichmay be connected to the usual 110 volt A. C. source.

On the inner leg of each saturable core, there is provided a winding 6which is supplied with variable current in the manner described here- 25inafter, to vary the flux density in the core and thus vary thereactance of the current-regulating device which, in turn, varies thecurrent supplied to the load devices 3 and 4. The windings l and 2 arearranged so that during any given so half cycle of the energizingcurrent, the current flowing in these windings sets up magnetic lines offorce in opposite directions in the two outer legs, with the result thatthe magnetic flux, due to the current in windings l and 2 traversesa aloop, as indicated by the arrows, without entering the inner leg.Obviously, the components of the flux oppose one another insofar as theinner leg is concerned, as is well understood in the art.

A transformer T has its primary winding P connected to the A. C. sourceand is provided with a plurality of secondary windings for supplying thenecessary voltages to the tubes V1 and V2. Preferably, each of thesetubes comprises a double-diode rectifier, thus providing full-wave 5rectification of the current supplied to the transformer T from thesupply source. The secondary winding S has its extremities connected tothe anodes of the tubes as illustrated, while its center tap isgrounded. The secondary windings S2 and S3 serve to suppy current to theenergizing circuits for the filaments or heaters of the tubes. Each ofthe relays R1 and R2 comprises contacts 1 and 8 which are included inthe energizing circuit for the filament of the associated tube. The

winding of each relay has one extremity grounded, while its otherextremity is connected to one end of the winding 6 of the associatedcurrent regulator. The other end of the winding 6 is connected to thecathode of the associated tube.

Since the operation of each of the devices or units A and B is the same,it is only necessary to describe the operation of one of these units,Considering the unit A, for example, and assuming that the tube V1 is inthe cold condition, the relay contacts I and 8 are closed so that whenthe transformer T is energized, the filament of tube V commences toheat. At this time, the current supplied to the load devices 3 and 4 isat its minimum value and is limited by the reactance of the windings Iand 2 and the associated core, there being no current flow throughwinding 6. As the cathode of tube V1 becomes heated, it

, emits electrons and its electron emission graduing S1 to ground andthence through the winding of R1 and winding 6 to the cathode. Theincreasing current fiow through the winding 6 increases the flux densityof core C1 substantially to the saturation point and thus decreases thereactance of the current regulator until the current supplied to theload devices 3 and 4 is increased to a predetermined high value.' Atthat time, the magnitude of the current flowing through the relaywinding is suflicient to operate the relay, thereby opening theenergizing circuit for the filament or heater of tube V1. Consequently,the cathode of the tube commences to cool, thereby effecting a gradualreduction of the space current flow through the relay winding andthrough winding 6. Hence the flux density of core C1 is. graduallyreduced, thereby gradually increasing the reactance of the currentregulator and eflecting gradual decreasing of the current supplied tothe load devices 3 and 4. Since much less current is required tomaintain the relay R1 energized than is required to energize it, therelay holds the energizing circuit for the filament of V1 open for asubstantial period of time. When the space current flow through thewinding of R1 has decreased to a low value, the relay is deenergizedpermitting contacts I and 8 to close and thereby reenergizing thefilament circuit of tube V1. The cycle then repeats itself.

Thus, the-current supplied to the load devices 3 and 4 graduallydecreases and increases cyclically between two predetermined values.Obviously, the irequencyof the cyclic operation will depend upon thedesign of the apparatus and, more particularly, upon the heating andcooling rate of the filament and cathode of tube V1 and also upon thedesign of relay R1. Obviously, the

frequency may be varied not only by varying the design of the apparatusbut also by the employment of well-known expedients, ior example by theuse of a variable resistor in the filament circuit of the tube to varythe current flow therein or by the use of time delay circuits of knowncharacter. If desired, the relay may have a time delay characteristic toretard its switch closing operation.

While the apparatus is applicable for any use, it is particularlyadapted to provide various lighting effects. By providing a plurality ofunits, such as the units A and B, and assigning different colors to thelamps controlled thereby, and by causing the devices to operate atdifferent irequencies, it will be apparentthat various color lightingeffects may be obtained. Thus, in Fig. 1 the frequencies of the twounits may be made different by employing tubes having different heatingand cooling characteristics or by enipioying any other well-knownexpedient such as above mentioned. Where it is desired to have a fixedcolor sequence, the frequencies may be adjusted accordingly. Thepossibilities of such a system are substantially unlimited, particularlyin the cyclic blending or changing of color combinations. It will beunderstood that the invention contemplates the employment of one unitalone or the employment of any desired number of units for controllingany number of circuits regardless of the specific character of the loaddevices included in such circuits.

- Obviously the relay R1 or R2 may be connected for voltage operationinstead of for current operation. For example, the relay winding couldbe connected in shunt with winding 6 instead of in series therewith.

It will be apparent also that a single double acting relay could be usedto control both units of Fig. 1, such relay having front and backcontacts and a single armature so that the tubes V1 and V2 would beenergized alternately. Such a modification of the apparatus is shown inFig. 3 wherein the double-acting relay R11 controls the filamentenergizing circuits of both of the tubes V1 and V2. The contacts l2control the filament circuit of tube V1 while the contacts l3 controlthe filament circuit of tube V2. It will be apparent that in thisinstance the filaments are energized alternately and cyclically, and thespace currents of the tubes are varied cyclically and differentially,thus effecting corresponding variation of the current in the workcircuits.

Further, the tube of either or both units may be alternately energizedand deenergized by any suitable means other than a relay.

.In Fig. 2, there is illustrated a modified form of the invention whichmay be used to advantage under certain conditions, for example whensubstantial amounts of power are involved. In this instance, theload-controlling reactor is directly controlled by the grid-controlled.vacuum tube V4 which, in turn, is controlled by the diode rectifier tubeVa, as will be explained in detail presently. The heater element of tubeV; is energized from the secondary winding S4 of the transformer T1 andthe energization of this tube is controlled by the relay R1. The anodeof tube V3 is connected through the secondary winding S5 and through thewinding of relay R3 to the grounded resistor R and to the control grid01 tube V4, It will be seen that the space-current circuit of tube V:extends from the anode through winding and resistor R to ground andthence to the cathode of the tube.-

The grounded filamentary cathode of tube V4 is energized from thesecondary winding S6. The anode of this tube is connected through thecontrol winding 9 on the saturable magnetic core Ca and through thesecondary winding S1 to ground.

The load circuit being controlled includes the series connected windingsII and [I on the core C: so that the magnitude of the current in theload circuit is variable by means oi the control winding Q, as'will beunderstood from the above description.

Considering the operation of this device, when the contacts of relay R:are closed as illustrated, the tube V3 is energized, causing anincreasing space-current flow through the space-current circuit of thetube, including the relay winding and the resistor R. Consequently, anincreasing negative bias voltage is built up across the re sistor Ra'nd;since,this voltage is applied between the grid and cathode of tubeV4, it serves to decrease the plate current of the tube flowing throughthe control winding 8. As a result, the flux density in the magneticcore 0: is decreased, thereby increasing the reactanceoi. the reactorwhich, in turn, decreases the magnitude of the current flowing in theload circuit.

When the space current 01' tube V: is of sutficient magnitude toenergize relay R3, the tube V: is deenerglzed and the space current ofthe tube diminishes. Consequently, the negative bias across resistor Rdecreases, causing the plate current of tube V4 to decrease. Theincreasing current flow through winding 8 increases the flux density ofthe core C3, thereby decreasing thereactance of the reactor which, inturn, causes the current in the load circuit to increase in magnitude.

Thus, it will be seen that the magnitude oi the current in the loadcircuit is caused to vary cyclically between predetermined low and highvalues. It .will be noted that the space current of tube V: controls therelay R: to thus control the energization of tube V: and also controlsthe bias across resistor R to thus-control the plate current of tube V4which, in turn, controls the reactance of the reactor.

While a single unit has been shown in Fig. 2. it will be understood thatany desired number of such devices may be employed to control diflerentload circuits and varying eflects or results may be obtained, asmentioned above in connection with Fig. 1. 7

Although certain embodiments of the invention have been illustrated anddescribed for the purpose of disclosure, it will beunderstood thatvari-.

one other ,embodiments and modifications are possible without departingfrom the scope oi the invention.

I claim:

1. In combination with an electric power supply and a work circuit, animpedance having a control winding, the terminal voltage of saidimpedancevaryinginresponsetochangesinthe magnitude of current in saidcontrol winding, a circuit connectingsaid power supply to said workcircuit through said impedance, an electrical discharge tube having afilament which has an appreciable thermal lag whereby the currenttherethrough is dependent upon said lag, a space current circuit forsaid tube, an energizing circuit for said filament, a relay having awinding.

in said space current circuit and contactscontrolledbythereiaywindingandarrangedin said energizing circuit tocontrol the same, whereby the space current of said tube is caused tovary cyclically, and means for varying the magnitude of current in saidimpedance winding in correspondence to the cyclic variation of saidspace current, whereby the terminal voltage of said impedance is causedto vary cyclically to thereby vary the current in said work circuitaccordingly.

2. In combination with an electric power supply and a work circuit, animpedance having a control winding, the terminal voltage of saidimpedance varying in response to changes in the magnitude of current insaid control winding, a circuit connecting said power supply to saidwork circuit through said impedance, an electrical discharge tube havinga filament which has an appreciable thermal lag whereby the currenttherethrough is dependent upon said lag, a space current circuit forsaid tube, on energizing circuit for said filament, means forcontrolling said energizing circuit so as to cause heating or cooling ofsaid filament, means associated with said space current circuit foroperating said controlling means so as to effect cooling of saidfilament when the space current reaches a predetermined amplitude and toeiIect heating of said filament when the space current decreases .to apredetermined low amplitude, whereby the space current of said tube iscaused to vary cyclically between said amplitudes, and-means for varyingthe magnitude of current in said winding in correspondence to the cyclicvariation 01' said space current, whereby the terminal voltage of saidimpedance is causedto vary cyclicallytothereby vary the current in saidwork circuit acoordinsly.

In combination with an electric power supply and a pair of workcircuits, a pair oi. impedanceseach having a control windingassociatedrespectively with said work circuits, the terminalvoltageoteachsaidimpedancevaryinginresponsetochangesinthemagnitude ofcurrent in said control winding, circuits connecting said power supplyto said work circuits through said im, a pair at electrical dischargetubes respectively with said impedances, eachsaid tubeha afilamentwhichhas an appreciable th lag whereby the currenttherethroughisdependentuponsaidlag,aspacecurrentcircuittoreachtubaanenemisingcircuit i'oreachfilamentadouble-acting relayhavingawindinginoneofsaidspacecurrentdrcuitsandhsvingcontactsinonefilamentenergizingcircuit and other contacts in the other filament energizing circuit,whereby said filaments are alternately and cyclicallyandthespacecurrents ofsaidtubesarevsried cyclically and differentially,andmeans for varying the magnitude of current in each saidimpedancewindingincorrespondencetothecyolicvariationofthespacecurrentintheassodated tube, whereby the terminalvoltages of said impedancesarecausedtovary'cyclicailysnddif-Ierentiallytotherebyvarythemrrentin said workcircuits.--

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